This invention relates to a communication network in which node devices to each of which a plurality of terminals have been connected are connected by parallel multiplexed transmission lines, as well as to a method of controlling this communication network.
The need to handle greater quantities of information has made it necessary to increase the speed and capacity of networks which connect terminal equipment. To achieve this, network systems in which node devices are connected by parallel multiplexed transmission lines have been studied. Such node devices and a network system which uses them will now be described.
FIG. 1 is a diagram useful in describing the principle of communication of a network system of the kind mentioned above. The network system includes node devices 101xcx9c104 having exchange switches 105xcx9c108 and buffers 109xcx9c112, respectively, terminals 121xcx9c136, and parallel transmission lines A, B, C, D which construct a ring. The communication principle of the network system shown in FIG. 1 will now be described.
The plurality of parallel transmission lines A, B, C, D of the network are interconnected by the exchange switches 105xcx9c108. Each terminal is connected to one of the parallel transmission lines among the lines A, B, C, D. In a case where one terminal connected to one parallel transmission line communicates with a terminal connected to another parallel transmission line, communication is carried out by switching the first-mentioned terminal to the other parallel transmission line at least one time by any exchange switch. Though the position at which switching is performed is not specified, communication control is facilitated if it is so arranged that the changeover is made to the transmission line of the destination at the node immediately preceding the destination node, with the transfers to arbitrary transmission lines being made at other nodes. In order to simplify the node devices, the exchange switches 105xcx9c108 of the network change the input/output connection relationship at a fixed period in accordance with a specific cyclic pattern irrespective of the input signals. After the input signals have been stored temporarily in the buffers 109xcx9c112, packets are read out of the buffers when the input/output connection relationship of the exchange switches has attained a desired relationship. This is the manner in which the network performs switching.
For example, in a case where a packet is transmitted from the terminal 122, which is connected to the node device 101, to the terminal 132 connected to the node device 103, the packet output by the terminal 122 is stored in the buffer 109 of the node device 101. When an input terminal IN2 of the switch 105 is connected to, say, an output terminal OUT2, the packet is read out of the buffer and output to the transmission line B. The buffer enters the buffer 110 of the node device 105. When the input terminal IN2 and output terminal OUT4 of the switch 106 are connected, the packet is read out of the buffer 110, whereby the packet is output to the transmission line D and sent to the terminal 132.
Thus, communication is carried out by transferring the packet to any parallel transmission line at each node device.
In a case where a broadcast is made from a certain transmitting terminal to all other terminals in the example of the prior art described above, connections must be established for all terminals. Since this increases the burden upon the transmitting terminal and network, the conventional system is impractical.
Accordingly, an object of the present invention is to provide a network system and communication method in which the burden upon the transmitting terminal and network is reduced.
According to the present invention, the foregoing object is attained by providing a first network system for connecting a plurality of node devices by a plurality of parallel transmission channels and connecting terminals to respective ones of the plurality of transmission channels via the node devices, each of said node devices comprising:
memory section for temporarily storing transmission data by allotting the transmission data to a plurality of storage areas that correspond to respective ones of the plurality of transmission channels;
transmitting section for transmitting the data, which has been stored in said memory section, upon selecting any of the plurality of transmission channels; and
memory control section for controlling said memory section so as to read out the data that has been stored in the storage area that corresponds to the transmission channel that has been selected by said transmitting section;
said memory section having distributing section for distributing broadcast data, which is data, contained in the data that enters said memory section, that is to be transmitted over the plurality of transmission channels, to the plurality of storage areas that correspond to the plurality of transmission channels that are to transmit the data, thereby duplicating the broadcast data.
According to the present invention, the foregoing object is attained by providing a second network system for connecting a plurality of node devices by a plurality of parallel transmission channels and connecting terminals to respective ones of the plurality of transmission channels via the node devices, each of said node devices comprising:
memory section for temporarily storing transmission data, said memory section storing broadcast data, which is data, contained in the data that enters said memory section, that is to be transmitted over the plurality of transmission channels, upon distinguishing this broadcast data from data other than broadcast data;
transmitting section for transmitting the data, which has been stored in said memory section, upon selecting any of the plurality of transmission channels; and
memory control section for controlling said memory section so as to duplicate the broadcast data by reading out the broadcast data repeatedly whenever said transmitting section selects any of the plurality of transmission channels, and transmit the broadcast data by the plurality of transmission channels.
The characterizing features of the first and second network systems are the fact that the broadcast data is duplicated in a node device and the fact that control is performed in such a manner that the broadcast data is transmitted over all of the plurality of channels involved in transmission. As a result, the broadcast data can be transmitted in such a manner that the data can be received by a plurality of destinations without establishing a connection for each and every destination.
In order to connect the transmission channels and terminals, the connection is made via separating section in the node devices. The separating section preferably has a function for distributing data, which enters from a transmission channel, to the downstream side of the transmission channel and to the side on which the terminal is connected. In particular, if the separating section has selecting section for selecting, in dependence upon information described in the input data, whether the input data is to be output to the side on which the terminal is connected without being output to the downstream side of the transmission channel, or whether the input data is to be output to the downstream side of the transmission channel without being output to the side on which the terminal is connected, or whether the input data is to be distributed to the downstream side of the transmission channel and the side on which the terminal is connected, then, when it is indicated that the input data is broadcast data and, moreover, data that has already been duplicated by another node device, the data is distributed to the downstream side of the transmission channel and to the side on which the terminal is connected, whereby broadcasting can be realized without requiring that broadcast data that has been duplicated at any node be duplicated for a plurality of channels at other node devices. Furthermore, the entered data can be output to the downstream side of the transmission channel when the entered data is not broadcast data and the data is not destined for a terminal connected to the separating means, and the entered data can be output to the terminal side when the data is destined for a terminal connected to the separating section.
When there are a plurality of the memory sections corresponding to each of the transmission channels that enter the node device, readout and writing can be performed at high speed. In order to change the transmission channel which connects the output from each memory section at this time, it is possible to adopt an arrangement in which the transmitting section has a switch for connecting the plurality of memory sections to mutually different transmission channels and for changing over the transmission channel to which each of the memory sections is connected, or an arrangement in which the transmitting section has a plurality of variable channel transmission sections capable of outputting the data, which has been stored in each memory section, by any of the plurality of transmission channels, and control section for controlling the plurality of variable channel transmitting sections in such a manner that the transmission channels which outputs data to the plurality of variable channel transmitting sections is different from one another.
It would be ideal for the plurality of transmission channels to be multiplexed by wavelength-division multiplexing or space-division multiplexing. If the plurality of node devices are connected in the form of a ring by the plurality of transmission channels, broadcast data duplicated by a node in an amount equivalent to the number of channels and output by this node returns to this node via all other nodes. As a result, broadcast data can be transmitted to all connected terminals.
According to the present invention, the foregoing object is attained by providing a communication method in a network system for connecting a plurality of node devices by a plurality of parallel transmission channels and connecting terminals to respective ones of the plurality of transmission channels via the node devices, comprising the steps of:
in a first node device, which is any one of said plurality of node devices, duplicating first data, which is data to be transmitted to a plurality of terminals, and outputting the duplicated first data over the plurality of transmission channels; and
in other node devices, outputting the first data, which enters over all of the transmission channels, to terminals connected to each of the transmission channels via these node devices per se, and outputting the first data over all of the transmission channels.
When broadcasting is performed by this method, broadcasting can be carried out without establishing connections for all destinations.
The plurality of node devices in this method are connected in the form of a ring by the plurality of transmission channels, and it would be ideal to arrange it so that the first data, which enters the first node device via the other node devices upon being duplicated by the first node device and output over all of the transmission channels, is terminated at the first node device.
Further, in order to facilitate the broadcast processing at each node device, an arrangement can be adopted in which the other node devices duplicate the first data entered by each transmission channel, output one by a transmission channel the same as the transmission channel over which the first data was transmitted, and output another one to a terminal connected to this transmission channel via its own node device.
Further, to duplicate the broadcast data, an arrangement can be adopted in which the first node device temporarily stores the duplicated first data, which corresponds to each one of all transmission channels, upon allotting the first data for every transmission channel, or an arrangement can be adopted in which the first node device temporarily stores the first data in advance, duplicates the first data by repeatedly reading out the temporarily stored first data and outputs the first data by all transmission channels.
Further, the first node device is a node device to which a terminal that transmits the first data is connected, a node device designated by a terminal that transmits the first data, or a predetermined node device among the plurality of node devices.